WDPN31 PGTW 232100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (MA-ON) WARNING NR
010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
INITIAL POSITION: 19.1N 118.8E
INITIAL INTENSITY: 50 KTS
GEOGRAPHIC REFERENCE: 322 NM SOUTHEAST OF HONG KONG
MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 16 KTS
SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS
FRAGMENTED DEEP CONVECTIVE WRAPPING INTO A PERSISTENT REGION OF
CONVECTION JUST WEST OF LUZON. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON THE EIR LOOP, ALONG WITH A MICROWAVE EYE
AS SEEN ON A WELL-TIMED 231753Z AMSR2 36GHZ IMAGE. UPPER-LEVEL
CONDITIONS REMAIN MARGINALLY FAVORABLE WITH MODERATE WESTWARD AND
FAIR EQUATORWARD OUTFLOW AND LOW TO MODERATE NORTHEASTERLY VERTICAL
WIND SHEAR. THE INITIAL INTENSITY OF 50 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON AN AVERAGE FROM PGTW, RJTD DVORAK ESTIMATES,
AUTOMATED DVORAK TECHNIQUES (ADT), AND SATELLITE CONSENSUS
(SATCON).

INITIAL WIND RADII BASIS: PERSISTENCE.

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T3.5 - 55 KTS
RJTD: T3.0 - 45 KTS
KNES: T3.5 - 55 KTS
CIMSS SATCON: 50 KTS AT 231659Z
CIMSS ADT: 49 KTS AT 231740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
VWS: 15-20 KTS
SST: 29-30 CELSIUS
OUTFLOW: MODERATE WESTWARD
OTHER FACTORS: FAIR EQUATORWARD OUTFLOW.

ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: MEDIUM
INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TS 10W WILL CONTINUE TRACKING TO THE
WEST-NORTHWESTWARD THROUGH TAU 72 AS IT REMAINS UNDER THE DIRECT
INFLUENCE OF THE SUBTROPICAL RIDGE (STR) OVER CENTRAL CHINA. THE
SUBTROPICAL RIDGE (STR) WILL REMAIN THE MAIN STEERING MECHANISM UNTIL
AFTER MA-ON MAKES LANDFALL NEAR YANGJIANG, CHINA. DURING THE NEXT 12-
24 HOURS, TS 10W IS EXPECTED TO GAIN HIGHER INTENSITY WHILE IT DRAWS
MORE ENERGY FROM THE VERY WARM (29-30C) SST AND DEEP OCEAN HEAT
CONTENT (OHC) OF THE SOUTH CHINA SEA. JUST AFTER REACHING ITS PEAK
INTENSITY OF 65 KNOTS, MA-ON WILL MAKE LANDFALL NEAR YANGJIANG,
CHINA, AND BEGIN TO DISSIPATE AS IT ENCOUNTERS HIGHER SHEAR AND
INTERACTS WITH THE RUGGED TERRAIN.

MODEL DISCUSSION: THE LATEST JTWC TRACK FORECAST REMAINS HIGHLY
CONSISTENT WITH THE PREVIOUS JTWC TRACK FORECAST. NUMERICAL MODELS
ARE IN TIGHT AGREEMENT WITH A NARROW SPREAD FROM 35NM AT TAU 12 AND
GRADUALLY SPREADS TO 110NM BY TAU 72, LENDING HIGH CONFIDENCE IN THE
OVERALL JTWC TRACK. THERE REMAINS ONLY MEDIUM CONFIDENCE IN THE
JTWC INTENSITY FORECAST WITH GFS AND COAMPS-TC INDICATING A PEAK
INTENSITY AT 70 KNOTS. HOWEVER, OTHER INTENSITY AIDS ARE REMAINING
LOWER AT THE 60-65 KNOTS AS THE PEAK, LENDING OVERALL MEDIUM
CONFIDENCE IN THE OVERALL JTWC INTENSITY.

FORECAST CONFIDENCE:
TRACK 0 - 72 HR: HIGH
INTENSITY 0 - 72 HR: MEDIUM//
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